Why do people give autistic people a hard time, especially autistic adults?

I mean just because I’m an adult doesn’t autism goes away (unfortunately). Like when kids show their autistic traits, some people find it weird but most thought it’s so cute but it’s an adult people criticize them. I got yelled at and called out for being “lazy” and “inconsiderate about others” and still “don’t get it”. When my mind wanders off, I get snapped at and told off about it.
When autistic kids get the attention, I don’t get the same attention anymore. They would say “Good job!” Or “Come on buddy!” But to me they just look at me weird.
I get yelled at to “move it” or “pay attention!”
When I say “Hi” or “what’s up.”I get ignored or get a plain “Hi” and focused on the kids more. I mean it’s supposed to be like that and kids go first, but don’t ignore me.
When I made an art project, all I got was an “Ok” “Okay and?” or no response. When the kids did they adults were like “Cool!” “That is beautiful! Great job!” “Way to go!”
Really? Why didn’t I get that same reaction?